Remove dead DocumentState metrics tracking code

content/common/navigation_params.h

Index: content/common/navigation_params.h
diff --git a/content/common/navigation_params.h b/content/common/navigation_params.h
index d6a0b79be4263eb6a603266ddcbb8ab074fa7287..ec5ec419118524efed1c9ebb93fdd39c62d59a8a 100644
--- a/content/common/navigation_params.h
+++ b/content/common/navigation_params.h
@@ -217,7 +217,6 @@ struct CONTENT_EXPORT RequestNavigationParams {
   RequestNavigationParams(bool is_overriding_user_agent,
                           const std::vector<GURL>& redirects,
                           bool can_load_local_resources,
-                          base::Time request_time,
                           const PageState& page_state,
                           int nav_entry_id,
                           bool is_same_document_history_load,
@@ -248,11 +247,6 @@ struct CONTENT_EXPORT RequestNavigationParams {
   // resources.
   bool can_load_local_resources;
 
-  // The time the request was created. This is used by the old performance
-  // infrastructure to set up DocumentState associated with the RenderView.
-  // TODO(ppi): make it go away.
-  base::Time request_time;
-
   // Opaque history state (received by ViewHostMsg_UpdateState).
   PageState page_state;